Passive tension in rat hindlimb during suspension unloading and
recovery: muscle/joint contributions.
Gillette, Patricia D., and Ronald D. Fell.
Department of Physiology and Biophysics, School of Medicine,
University of Louisville, Louisville, KY 40292 and Department of
Biology, University of Louisville, Louisville, KY 40292
APStracts 3:0179A, 1996.
Muscle/joint stiffness associated with disuse conditions or
weightlessness may seriously impair movement and work capacity. The
purpose of this study was 1) to develop a noninvasive model to
measure rat hindlimb passive tension, 2) to describe changes in
passive tension (i.e., flexibility) during whole body suspension (S)
and weight bearing recovery and, 3) to determine relative
contributions of the posterior hindlimb to passive tension. Male
Sprague-Dawley rats were suspended (14 days) and re-loaded (14 days).
On days 0, 7, 14, 17, 21, and 28, animals were anesthetized and
hindlimb passive tension was measured during ankle dorsiflexion.
Seven days of S significantly increased passive tension. Recovery of
passive tension occurred by 14 days of weight bearing. In S animals,
increased passive tension was due to musculo-tendinous units (75%)
rather than the joint (25%). Increased passive tension did not appear
to be due to a shorter muscle, but changes in muscle architecture,
cytoskeletal proteins, or viscoelastic properties of the muscle and
its connective tissue elements cannot be excluded.
Received 10 August 1995; accepted in final form 21 March 1996.
APS Manuscript Number A875-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 16 April 96